[MCPE-81987] Rails aren't always powered correctly

Rails sometimes aren't powered correctly and large sections of rail can be left unpowered.

Steps to reproduce

Build this:
[media]
Be sure to put the lever on the side of the block toward the front of the picture, not on the top of the block.

Expected results

The farther away block in the picture activates 8 more rails beyond it.

Actual results

The blocks beyond the farther away block are not activated. However, if you put the lever on top of the closer block instead, or if you place a rail next where the lever is in the picture, then the farther away block does activate 8 more rails beyond it.

Notes

Related to MCPE-81981

I believe this is a problem with the power sources calculating what they're powering, not the rails, as with 2 power sources it works.

Note that this is not related to chunk borders.

Linked issues

relates to 2

MCPE-105749 Rails powered by an Unpowered-Source. Open

MCPE-81981 Issues with how signal strength is calculated and displayed Resolved

Attachments

Apparent powering paradox.mp4

powered rails' power shifting backwards.mp4

Powering paradox.mp4

Comments 17

Tal Melamed 2020-06-04T04:18:52Z

Is it happening next to chunk boarder only?

77Tigers 2020-06-04T18:22:02Z

no, it happens anywhere in the world.

GoldenHelmet 2020-06-05T08:40:50Z

I am not able to reproduce this in 1.14.60. When I build what is shown in the picture, the second block powers 8 more rails beyond its position. I’ve tried several combinations of block placement order and using commands vs regular block placement. Is there a special process you used to set up what is shown in the picture?

77Tigers 2020-06-05T17:02:29Z

I assumed this affected 1.14.60, because 1.14.60 was affected by a similar issue, but perhaps not.

EDIT: just asked someone to test and it does in fact affect 1.14.60

The lever has to be on the side of the block btw. It may well be directional. There's no special process I used to set it up.

GoldenHelmet 2020-06-05T19:51:04Z

Ok I've reproduced it now. I must have had the lever on top of the block.

It looks like the game begins power mapping from a producer and then when it finds a connection to a powered rail it activates 8 powered rails in each direction from the powered rail that makes the shortest connection to the producer. That's at least logical and limits each producer to activating a maximum of 17 rails (rather than 44 or so), although it does create some strange behavior, see

[media]

What I can't explain is why, in the picture you've shared, the lever on the side of the block causes only that block to be treated as a producer for powered rail activation, while putting a lever on top of the block causes the block downstream to be treated as a producer. This is what I'd say is the real bug:

[media]

And this is where I see a real paradox:

[media]

7 more comments

77Tigers 2020-06-05T21:43:01Z

That is really wierd. It looks like direct contact with the lever from the rails stops this issue from occuring.

Because the issue only occurs when powering a block from the side (as far as I know), I linked it to MCPE-81981. There are other issues with powering blocks from the side.

I would also like to point out that rails are powered slightly differently than usual, because of the fact that you can power multiple rails at once.

77Tigers 2020-06-05T21:56:00Z

I think I see what happened there now. If you power any of the unpowered rails with that same power source then it will still work. Placing a rail there results in one more rail becoming unpowered and powered by the redstone line instead, as seen in this video

[media]

Eyeth 2020-06-05T22:52:07Z

I was able to reproduce in east and west directions.

GoldenHelmet 2020-06-06T12:22:48Z

You can power 49 rails with 1 lever:

[media]

GoldenHelmet 2020-06-06T13:30:42Z

Amending my earlier finding,

It looks like the game begins power mapping from a producer and then when it finds a connection to a powered rail it activates 8 powered rails in each direction from the powered rail that makes the shortest connection to the producer.

What I think actually happens is

The producer activates the powered rail that has the shortest connection path to that producer,
then that powered rail activates 8 powered rails in each direction,
and then the game ignores any other connections from that producer to those 17 rails.

In the original picture shown in the description, the downstream block is at the 8th powered rail from the powered rail activated by the powered block, so it is ignored. When you place a powered rail next to the lever, then the lever activates that powered rail directly (since that's now the shortest path to a powered rail), the powered block is ignored, and the downstream block is then at the 9th powered rail, so it is no longer ignored.

This still doesn't explain why putting a lever on top of the block instead of the side changes things. That may be where MCPE-81981 comes in.

Tal Melamed 2020-06-11T19:49:37Z

I am not able to reproduce this in 1.16.0.67...

77Tigers 2020-06-11T20:33:43Z

Have you tried doing it in different directions? If it is fixed, that would be great.

EDIT: can reproduce in 1.16.0.67

Tal Melamed 2020-06-11T21:12:45Z

Yes, tried in different directions.

77Tigers 2020-06-27T21:24:46Z

still affects 1.16.20.50

GoldenHelmet 2020-06-27T22:05:13Z

@@unknown you can, and should, update the affected versions field yourself on your own tickets.

Natthan 2020-08-28T01:01:05Z

has this been fixed or not?

GoldenHelmet 2020-08-28T11:39:23Z

It is supposed to be fixed in the current beta. The ticket will be resolved when the fix is included in a release version.